soc: qcom: Add a config flag to know the build variant

Add a Kconfig flag to differentiate between a GKI and an Non GKI build.
CONFIG_QGKI is enabled if the build is a Non GKI variant (QGKI or debug).
This flag doesn't differentiate between QGKI and debug variants.

Change-Id: I6b53b1e0e4c071fc7d9b365ff374ffe4e8b3e8ba
Signed-off-by: Prakruthi Deepak Heragu <pheragu@codeaurora.org>